FIG. 4.

Cdc2 kinase activity is suppressed during G₂/M transition in HR′Vpr-infected cells. (A) HeLa cells (1.5 × 10⁵) were synchronized at G₁/S by a double thymidine block. They were then infected with equivalent amounts of HR′Vpr or HR′Thy (0.3 μg of viral p24). Whole-cell lysates were prepared at different time points after infection. Cdc2 was isolated from lysates, and the kinase assay was performed in the presence of histone H1 substrate. Proteins were resolved by SDS-12% PAGE and detected by Western blotting with anti-Cdc2 and anti-phosphorylated Cdc2 antibodies. P.I., postinfection. (B) Cdc2 kinase activity after normalization by the amount of Cdc2. The activity obtained 14 h after infection with HR′Thy was arbitrarily set to 100%.